Hoping for a bit of input here as my AC voltage knowledge is somewhat limited.
I have a 12 X 36 Lathe with a single phase 2HP motor. Today while running some parts I became aware that the reverse feature is no longer functioning.

It runs fine in the forward direction. When trying to start the motor in reverse i can see the fan blades move a little as though it's trying to start but then it stops and just hums. I tried giving it a spin to see it that might help and it did not.

Time for a new motor ??? 400.00 OUCH !!! Any input/ help appreciated
Tim

Look for start capacitors. Replace those exactly as they are now. Then try it...

Would there be different start capacitors for forward and reverse ???
the reason I ask is it starts and runs fine in the forward direction

I believe there is just a run capacitor. The motor needs the polarity reversed to turn it the opposite direction. Being 220 and reversible the motor may have 4 to 6 wires. The switch has multiple contacts and is should we say is the control or computer. If any contact is pitted the motor will try but not be able to spin. You could try to see if you can see into the switch. Contact cleaner and giving the switch a rapid work out may bring it to life. Also make sure a breaker is not popped. Some designs may let the motor run on one leg but not allow any direction changes.

thanks to both responders

I will do that first thing in the AM, Anybody else ?

Switch contacts dirty, run some Emory cloth over the contacts. Sounds like one leg of the 110 isn’t conectng.

Make sure you unplug it first

Switch contact(s) is(are) dirty or damaged. The wiring diagram below illustrates how the reversing function works by switching two of the motor leads. I would be careful of using common emery cloth to clean electrical contacts. True emery cloth leaves hard debris on the contacts that leads to future contact burning. If the contacts are large, I use a common point file. If they are small, I'll use aluminum oxide sheet or roll abrasive.

Thank you all very much, I will check and report back

Might be a bearing, I've had them work fine froward but in reverse the shaft jams.

Unfortunately as near as i can tell at this time it appears to be the motor . Getting to it to actually measure the Voltages is a royal PITA. But i will do so before replacing it once the new motor is here. I will report back
Thanks to all that responded

I'll keep you posted
thanks again

Well if it’s the switch (has nothing to do with motor) you’ll still have the problem and out money and time.

I'm not buying that. Forward and reverse use the same windings and the same caps. Only the polarity of the start winding gets reversed.

If its in the motor then its a connection issue. I suspect a bad connection in the wiring system, and as stated, most probably in the switch.

A single phase motor has no starting torque and has no idea which direction to rotate. A start capacitor is used in a start winding to electrically phase shift the start winding in respect to the run winding. This phase shift allows the motor to have starting torque and defines motor rotation direction. By reversing the polarity of the start winding the phase shift is now in the other direction and motor rotation is reversed.

There is always a chance it could be in the motor, but the chances are slim............

I agree too

Well i will find out when the new one arrives and I gain access to the motor and electrical panel. The forward / revervse switches that I was able to access are 24VAC. They control two contactors that send the power to the motor. This is all per their Tech guy and the schematic that I have which leaves a bit to be desired.
He claims in 25 years they have not had a contactor fail unless the coil went bad. This one is Audibly working. He also stated that if it were a switch problem the contactor would be not be audibly clicking nor would the motor be trying to start.
I understand DC pretty well but get lost real fast on the AC stuff.

I understand the part about 110V AC and it reversing direction 60 times a minute.
I understand that two legs of of 110 together make the 220. Beyond that is where I start getting lost. Especially when you guys start talking about reversing the polarity, my head goes into a tailspin

I sincerely appreciate everyone's assistance and trying to help. It would be a lot better if I could access the backside without the PITA it's going to be. i will definitely keep everyone posted

What's confusing you is that someone is using DC terms (polarity) when referring to AC.

there is no polarity in an AC circuit, there is phasing though. I suppose if you want to be real technical about it AC is constantly changing it polarity as a function of it's action, but talking about AC polarity is like saying water is wet and not relevant to how is makes a motor work.

Pure AC is a nice sine wave, you've seen them even if you don't know it. Single phase shown.



All phases will look the same, or near enough, in frequency and amplitude.

What changes in multiphase power is when the peaks occur in time in relation to each other. By shifting that peak in time you can reverse the motor and that's what starting caps do when starting a single phase motor.

Two phase sine wave shown.



In a three phase motor you just swap two of the phases as wired to the motor, this is done with a switch of some sorts.

So in the pic below, wired A, B, C runs one way, A, C, B runs the other way



You can have more than three phases, but the ones I talked about are the three most common setups you will see.